Defrosting system



y 1942- A. F. HOESEL 2,281,770

DEFROSTING SYSTEM Filed Jan. 17, 1941 &

- 2o 1 9 4l L Inventor Patented May 5, 1942 DEFBOSTING SYSTEM Anthony F.Hoesel, Chicago, 111., assignor to Peerless of America, Incorporated,Chicago, Ill.,

corporation of Illinois Application January 17, 1941, Serial No. 374,885

4 Claims. The present invention relates to hot gas defrosting of coolingunits which are utilized to cool compartments to temperatures below 32F.

More specifically the invention contemplates the use of the refrigerantcompressor hot gas discharge in order to supply sufficient heat to thecooling unit in order to defrost-the same. It also contemplates the useof means whereby the time functioning of such defrosting system is underthe adjustable control of manually operated time switch means, wherebythe operator may manually initiate the various necessary functions, forthe defrosting, by merely flipping a switch handle to a given timedesignation previously determined as being suflicient to complete thedefrosting cycle. Upon the elapse of the given time, the refrigerationsystem then automatically resumes its previous normal operation.

While the use of hot compressor discharge gas, for defrosting, is ratherold in the art, all previous systems necessitated manual attendance tostart and stop the various necessary functions in a somewhat givensequence, and

then after the lapse of sufficient time, to then reverse the previousoperations so that the system would then be in normal function.

An object, of the invention, is to provide an improved system ofsemi-automatic hot gas defrosting of low temperature cooling units.

Another object, of the invention, is to provide means for vaporizing,before entrance into the compressor, of the returned refrigerant fluid,which is condensed in the cooling unit due to its surrender of heatthereto.

Other objects, of the invention, will be more fully disclosed in thefollowing specification and claims:

In the drawing, the figure is a diagrammatic elevational view of arefrigerating system embodying the invention.

Referring to the drawing, a cooling unit 2, comprised of a nestedvolatile refrigerant conduit circuit 3 upon which fins 4 are mounted inheat transfer relationship, is situated within a casing 5 through which,and over the exterior surfaces of the cooling unit 2, a fan 6, driven bythe motor 1, forces an air circulation as indicated by the arrows.

The casing 5 has a drain 8, usually connected to a sewer, to get rid ofthe defrosted moisture during the defrosting period.

The refrigerant compressor 9 is driven by means of the motor I 0 andevacuates refrigerant fluid, in vapor phase, from the conduit ll.

The compressed vapor is forced into the discharge 'conduit I2 fromwhence it enters a condenser l3, wherein, during normal functioning, itsurrenders its heat and becomes condensed to its liquid phase. Theliquid receiver I4 receives this liquid, which is then led by means ofthe liquid conduit l5 to an expansion valve it which tends, duringnormaloperation, to feed refrigerant fluid, under reduced pressure, tothe refrigerant inlet conduit I! connected to the conduit circuit 3. Asuction conduit It serves to lead the refrigerant fluid from the outletof the conduit circuit 3.

Interposed, between the suction conduit I8 and the conduit II, is ahollow casing I9 containing an electrical heating element 20, whosefunction will be described later.

The discharge conduit [2 and the refrigerant inlet conduit ll areconnected by means of the bypass conduit 2| in the circuit of which isplaced a solenoid valve 22.

The above comprises the refrigerant circulation system.

An electric timing switch 24, of which there are numerous suitable typescommercially available at present and so well known, in the art, that inthe present instance it is presumed sufficient to represent the samediagrammatically and with proper functional description, comprises acasing 25 containing clock mechanism, not shown, which is wound up bymeans of the timing handle 26 being moved in a clockwise direction sothat the pointer 21 stops at some particular predetermined point of thegraduated face, which is usually graduated in minutes of operation.

The timing handle 26 is shown in the stopped position. Assume it to bemoved to say the 5 minute graduation, then the timing handle graduallymoves counterclockwise so that at the lapse of 5 minutes the timinghandle 26 is again in its present stopped position.

Included within the casing 25 is a single pole double throw switchcomprised of stationary contacts 29 and 30 and a contact arm 3|oscillating, about the fulcrum 32, to establish an electrical circuitwith either contact 29 or .30 depending upon the position of the timinghandle 26.

Whenever the timing handle 26 is moved to on" position, clockwise, thecontact arm 3| swings to the right and establishes contact with thestationary contact 30. This contact persists until the timing handle 26returns to off position, as shown, at which time the contact arm 3! thenswings to the left and establishes contact with the stationary contact29, as shown.

The electrical conduits 35 and 36, leading to a suitable source ofelectrical energy, connect to the compressor motor ID. The electricalconduit 31 connects conduit 35 with the fulcrum 32 of the contact arm 3!which is in electrical circuit therewith.

An electricalconduit 38 connects with the conduit 36 and one side of thecoil circuit in the solenoid valve 22. The other side of the coilcircuit, of the solenoid valve 22, is connected to the stationarycontact 30 by means of the electrical conduit 39.

The electrical heating element 20 is connected to the electricalconduits 3G and 39 by means of the conduits l and ll respectively.

The fan motor I connects to electrical conduit 38 by means of theconduit 42, and also connects to the stationary contact 29 by means ofthe conduit 43.

The above comprises the electrical wiring systern.

With the timing handle 26 in the off position, as shown, the compressormotor I 0 and the fan motor 1 are in operation. The solenoid valve 22 isin closed position and the electrical heating element 20 is deenergized.

During the operation of the compressor 9 and the normal circulation ofrefrigerant within the refrigerant conduit circuit 2, there will occur aprogressive accumulation of frost upon the exterior surfaces of theconduit 3 and the fins 4 mounted thereon. After a sufficientaccumulation of frost, it will then become necessary to defrost thesesurfaces.

The operator now moves the timing handle 26, in a clockwise direction,for some predetermined time lapse. The contact arm 3| now swingsto makecontact with the stationary contact 31!. The fan motor 1 now stops andthe electrical circuit is now established in both the electrical heatingelement 20, which now heats up, and the solenoid valve 22, which nowopens.

The compressor 9, being still in operation,-

discharges hot compressed refrigerant vapor into the discharge conduit[2. Since the solenoid valve 22 is open, the hot compressed vapor passesthrough the conduits 2i and I! to the conduit circuit 3 in which itsurrenders heat, thereby sufliclently elevating the temperature of thecon-, duit 3 and flns [to defrost the same.

During this stage, the pressures in the conduit 3 become much greaterthan the normal, therefore no refrigerant liquid is fed through theexpansion valve l6, but the hot vapor condenses within the conduit 3 andeventually passes into the suction conduit 18 in liquid phase.

It is obvious that, if liquid refrigerant passes into the compressor 9which is conceded to be bad practice, it will among other deleteriousresults, naturally result in a reduced amount of work and thetemperature of the discharge, to "the discharge conduit i2, will be suchthat it will be incapable of being an efficient defrosting agent.

Since the returned refrigerant fluid is under the influence of the heatgenerated by the electrical heating element 20, any returningrefrigerant liquid will thereby become vaporized and the temperature ofthe fluid, passing through the conduit II and into the compressor 9,will be substantially the same. as that passing during normal operation.This ensures the compressor discharge fluid as being of such temperatureas will do eiiicient defrosting.

After the proper time lapse, depending upon the original positioning ofthe timing handle 26, the timing handle is automatically returned to itsoriginal position, as shown, and the contact arm 3| swings to andmakescontact with the stationary contact 29. The circuit, in the conduit43, is reestablished and the fan motor I again starts. The circuit, inthe conduit 39 is broken, thereby closing the solenoid valve 22 anddeenergizing the electrical heating element 20.

The system is now in normal operation until such time as it is desiredto again defrost the cooling unit. At such time, all the operator needsto do is flip the timing handle 26 to its proper time position, withoutgiving any part of the system any further attention, since it willalways automatically restore to normal function after the defrostingtime lapse.

From the above, it will be noted that I have provided a defrostingsystem which operates with a minimum of attention and which tends tomaintain a constant temperature of discharge fluid leading from thecompressor.

While the drawing and specification show a particular embodiment of theinvention, it is understood that various modifications may be employedwithout departing from the spirit and scope of the invention which is tobe limited only to the claims hereto appended.

I- claim:

1. The method of defrosting a cooling unit Upon the exterior surfaces ofwhich a progressive frost accumulation occurs during the circulation ofa volatile refrigerant therethrough by means of a compressor normallyevacuating refrigerant vapor from said cooling unit and discharging thecompressed vapor into a condenser wherein it surrenders heat and becomesliquified prior to again normally entering said cooling unit, whichcomprises periodically conducting the discharge of said compressor,prior to its liquefaction in said condenser, to the cooling unit whereinit tends to surrender heat, for the defrosting function, and becomesliquified and then reheating the liquid refrigerant, issuing from saidcooling unit, in order to vaporize the same before its entrance intosaid compressor, the said heated vapor being at substantially the samepressure as that obtaining within the cooling unit.

2. The method of defrosting a cooling unit upon the exterior surfaces ofwhich a progressive frost accumulation occurs during the circulation ofa volatile refrigerant therethrough by means of a compressor normallyevacuating refrigerant vapor from said cooling unit and discharging thecompressed vapor into a condenser wherein it surrenders heat and becomesliquefled prior to again normally entering said cooling unit, whichcomprises periodically conducting the discharge of said compressor,prior to its liquefaction in .said condenser, to the cooling unitwherein it tends to surrender heat, for the defrosting function, andbecomes liquefied and then reheating the liquid refrigerant, issuingfrom said cooling unit, in order to vaporize the same beforeits entranceinto said compressor.

3. In a mechanical refrigerating system having a cooling unit normallydischarging refrigerant vapor into ,a suction line conduit connected tothe inlet of a compressor normally discharging compressed vapor into aconduit concharging into a refrigerant inlet conduit of the coolingunit, over the exterior surfaces of which an air circulation ismaintained by a motor driven fan and upon which exterior surfaces afrost progressively accumulates, the combination of a by-pass conduitconnected to said compressor discharge, and ahead of said condenser, andalso connected to the refrigerant inlet between the said refrigerantpressure reducing means and the cooling unit, a normally closed solenoidvalve in said by-pass conduit, electrical heating means disposed in heattransfer relationship with the refrigerant passing through the suctionline conduit and normally de-energized, an electrical time switchnormally maintaining a current supply to the fan motor. manuallyoperated means to set said time switch for a given time lapse duringwhich the current suppl to said fan motor is interrupted, and duringwhich time lapse the time switch the solenoid valve to open positionallowing the compressor discharge fluid to enter the inlet of saidcooling unit, said time switch, during said time lapse, also energizingsaid electrical heat; ing means.

4. In a mechanical refrigerating system having a cooling unit normallydischarging refrigerant vapor into a suction line conduit connected tothe inlet of a compressor normally discharging compressed vapor into aconduitconnecting the compressor with a condenser from which arefrigerant liquid conduit leads to a refrigerant pressure reducingmeans normally discharging into a refrigerant inlet conduit of thecooling unit, over the exterior surfaces of which an air circulation ismaintained by a motor driven fan and upon which exterior surfaces afrost progressively accumulates. the combination 7 of a by-pass conduitconnected to said com-- pressor discharge, and ahead of said condenser,and also connected to the refrigerant inlet between the said refrigerantpressure reducing means and the cooling unit, a normally closed solenoidvalve in said by-pass conduit, electrical heating means disposed in heattransfer relationship with the refrigerant passing through the suctionline conduit and normally de-energized, an electrical time switchnormally maintaining a current supply to the fan motor, manuallyoperated means to set said time switch for a given time lapse duringwhich the current supp to said fan motor is interrupted, and duringwhich time lapse the time switch energizes the solenoid valve to openposition allowing the compressor discharge fluidto enter the inlet ofsaid cooling unit, said time switch} during said time lapse, alsoenergizing said electrical heating means, and the said-time switchautomatically reestahlishing said fan motor current circuit andde-energizing said solenoid valve and said electrical heating meansafter the time lapse.

ANTHONY F. HOESEL.

